view_cache_dependency API

A declarative API for specifying dependencies that affect template
cache digest computation. In your controller, specify any of said
dependencies:

  view_cache_dependency { "phone" if using_phone? }

When the block is evaluated, the resulting value is included in the
cache digest calculation, allowing you to generate different digests
for effectively the same template. (Mostly useful if you're mucking
with template load paths.)

1 files changed, 18 insertions, 0 deletions

diff --git a/actionpack/lib/action_controller/caching.rb b/actionpack/lib/action_controller/caching.rb
index 2892e093af..e31743bcc7 100644
--- a/actionpack/lib/action_controller/caching.rb
+++ b/actionpack/lib/action_controller/caching.rb
@@ -70,12 +70,30 @@ module ActionController
 
       config_accessor :perform_caching
       self.perform_caching = true if perform_caching.nil?
+
+      class_attribute :_view_cache_dependencies
+      self._view_cache_dependencies = []
+      helper_method :view_cache_dependencies if respond_to?(:helper_method)
+    end
+
+    module ClassMethods
+      def view_cache_dependency(&dependency)
+        self._view_cache_dependencies += [dependency]
+      end
+
+      def view_cache_dependencies
+        _view_cache_dependencies.map { |dep| instance_exec &dep }.compact
+      end
     end
 
     def caching_allowed?
       request.get? && response.status == 200
     end
 
+    def view_cache_dependencies
+      self.class.view_cache_dependencies
+    end
+
     protected
       # Convenience accessor.
       def cache(key, options = {}, &block)